1. Field of the Invention
This invention relates to a symbol string pattern recognition equipment for use in a pattern data processing system.
2. Description of the Prior Art
The recognition equipment is such that, in an input pattern recognition system, in which the class of an input pattern is determined by the relative arrangement of features, it receives each input pattern as a symbol string pattern, discriminates its class by the comparison with standard symbol string patterns based on the sequential logics, and thus it is indispensable to the recognition of hand-written characters.
As can be seen from the article entitled "NEC Automatic Mail Processing System", disclosed in the periodical NEC RESEARCH & DEVELOPMENT NO. 20 published in January, 1971, on Pages 100 to 109, the symbol string recognition equipment proposed hitherto are developed in the form of a special-purpose digital computer, in which a plurality of standard symbol string patterns are stored in a magnetic core memory. In this case, the number of the standard symbol string patterns required for obtaining a specific recognition ratio amounts to as many as several hundreds even in the case of the recognition of only 10 characters. The sequential comparison of a symbol string pattern from each input pattern with the standard symbol string patterns stored in the core memory continues, until the determination of the class for the input pattern has been given. As a result, the recognition processing time per input pattern depends on the product of the number of the standard symbol string patterns multiplied by the access time for reading out the respective standard symbol string patterns from the core memory, resulting in a considerably long time period needed for processing. As is apparent from the foregoing, the costly high speed core memory must be employed only for the purpose of recognizing the input patterns at not so high processing speed. Thus, the symbol string pattern recognition equipment in the prior art has several vital disadvantages in that the equipment must select one of the three possibilities, i.e., (i) adoption of a higher speed (and hence, further costly) core memory to cope with an increase in the number of characters to be recognized, (ii) compromise with the lowering in the processing speed and (iii) admission of the low recognition ratio.